The main focus of this proposal is on the cell membrane ion channels in airway smooth muscle. A knowledge of the mechanism of conductive ion movement and its regulation is essential to understand the normal function of airway smooth muscle and abnormalities in disease. To directly study the ion channels, both single-channel and whole-cell electrophysiologic measurements will be made using the patch clamp technique in single isolated smooth muscle cells. The work will focus on potassium and calcium channels. In both cases, the kinetic and conductive properties of the channels will be studied. A major effort will be to understand how the channels are regulated, both by hormones and neurotransmitters and by intracellular mediators. The majority of the work will be performed with canine tracheal smooth muscle, but human tracheal smooth muscle will also be used. The findings will increase our knowledge of how the airway smooth muscle cell membrane transports ions, thereby regulating, in part, contractility. Thus, they may have direct applicability to asthma.